Wax-based encapsulant/moisture barrier for use with electronics received in water meter pits

ABSTRACT

The presently disclosed subject matter is directed to an encapsulant for electronic components such as those utilized in AMR technology. The encapsulant comprises a wax, a tackifier, a polymer, a plasticizer, a thixotropic agent, and an antioxidant and is designed to protect electronic components from harsh environments such as those where high levels of humidity or corrosive liquids may be present. For example, the encapsulant exhibits minimal percent weight gain due to moisture vapor when subjected to temperatures ranging from about −40° C. to about 70° C. and relative humidities ranging from 0% to 85% over a period of 200 days.

FIELD OF THE SUBJECT MATTER

The presently disclosed subject matter relates to Automatic MeterReading (AMR) technology. More particularly, the presently disclosedsubject matter relates to an encapsulant that can be used to insulateelectronic components associated with AMR technology to protect thecomponents from harsh environments.

BACKGROUND OF THE SUBJECT MATTER

AMR technology used in conjunction with utility meters, and particularlywater meters, must generally operate in relatively harsh environments.For example, water meters and AMR components placed in water meter pitsare exposed to high humidity levels almost constantly. Additionally,meters and associated components placed into pits are potentiallysubject to corrosion due to contact with various corrosive liquids.Often designers try to design the meter components from materials thatare capable of withstanding exposure to moisture and/or corrosiveliquids. Another option is to hermetically seal the housings containingany electronic components, though this is often not a desired approachbecause of manufacturing constraints and high costs. Still anotherapproach is to try to insulate any electronic components associated withutility meters from harsh environments through the use of variousencapsulants or potting materials.

In cases where electrical components are located in harsh environments,a potting material or encapsulant with a decreased diffusion rate thatcorresponds with improved moisture protection and shields the componentsfrom corrosive liquids is thus desired. While silicones, polyurethanes,and epoxies have been developed as potting materials and can providesome protection against moisture, thermal shock, and vibration, suchpotting materials/encapsulants still allow for the penetration ofmoisture over time due to their higher permeability and diffusion rates.Thus, these materials do not sufficiently waterproof the electricalcomponents that they surround.

Prior publications that describe potting materials or encapsulantsinclude U.S. Pat. No. 7,999,016 to Osada et al. disclosing a“Semiconductor Encapsulating Epoxy Resin and Semiconductor Device,” U.S.Pat. No. 7,763,673 to Okamoto et al. disclosing a “Curable CompositionContaining a Silicon-Containing Group Polymer, a Titanium Chelate, andan Amide Wax,” U.S. Pat. No. 7,741,388 to Murotani et al. disclosing an“Epoxy Resin Composition and Semiconductor Device,” U.S. Pat. No.4,977,009 to Anderson et al. disclosing “Composite Polymer/DessicantCoatings for IC Encapsulation,” and U.S. Patent Application PublicationNo. 2010/0067168 by Summers et al. disclosing “Composite OrganicEncapsulants.” The complete disclosures of such patent publications arefully incorporated by reference herein for all purposes.

While various compositions have been developed for potting orencapsulating electronic components, and while some level of protectionfrom harsh environments has been provided, no particular composition hasemerged that encompasses all of the desired characteristics as hereafterpresented in accordance with the subject technology.

SUMMARY OF THE SUBJECT MATTER

In view of the recognized features encountered in the prior art andaddressed by the presently disclosed subject matter, an improvedwax-based encapsulant for use with electronics received in water meterpits has been provided.

The present disclosure contemplates an encapsulant for use withelectronic components used in automatic meter reading technologyoperating at temperatures of less than about 65° C. The encapsulant caninclude a wax, a tackifier, a polymer, and a plasticizer. Theencapsulant can exhibit a percent weight gain of only from about 0.001%by weight to about 1.5% by weight over a period of about 200 days whenthe temperature ranges from about −40° C. to about 70° C. and when therelative humidity ranges from about 0% to about 85%.

Additional objects and advantages of the presently disclosed subjectmatter are set forth in, or will be apparent to, those of ordinary skillin the art from the detailed description herein. Also, it should befurther appreciated that modifications and variations to thespecifically illustrated, referred and discussed features, elements, andsteps hereof may be practiced in various embodiments and uses of thepresently disclosed subject matter without departing from the spirit andscope of the presently disclosed subject matter. Variations may include,but are not limited to, substitution of equivalent means, features, orsteps for those illustrated, referenced, or discussed, and thefunctional, operational, or positional reversal of various parts,features, steps, or the like.

Still further, it is to be understood that different embodiments, aswell as different presently preferred embodiments, of the presentlydisclosed subject matter may include various combinations orconfigurations of presently disclosed features, steps, or elements, ortheir equivalents (including combinations of features, parts, or stepsor configurations thereof not expressly shown in the figures or statedin the detailed description of such figures). Additional embodiments ofthe presently disclosed subject matter, not necessarily expressed in thesummarized section, may include and incorporate various combinations ofaspects of features, components, or steps referenced in the summarizedobjects above, and/or other features, components, or steps as otherwisediscussed in this application. Those of ordinary skill in the art willbetter appreciate the features and aspects of such embodiments, andothers, upon review of the remainder of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the presently disclosed subjectmatter, including the best mode thereof, directed to one of ordinaryskill in the art, is set forth in the specification, which makesreference to the appended figures, in which:

FIG. 1 illustrates a utility meter pit configuration;

FIG. 2 illustrates an exploded view of an assembly including electroniccircuitry that may be present in AMR technology in utility meter pits;

FIG. 3 illustrates a perspective view of an electronic sub-assembly thatmay be present in AMR technology in utility meter pits;

FIG. 4 illustrates a meter endpoint circuit board coated with theencapsulant of the present disclosure; and

FIG. 5 illustrates a summary of the data comparing samples of the testedencapsulant of the present disclosure with corresponding controls.

Repeat use of reference characters throughout the present specificationand appended drawings is intended to represent same or analogousfeatures, elements, or steps of the presently disclosed subject matter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As discussed in the Summary of the Subject Matter section above, thepresently disclosed subject matter is particularly concerned with anencapsulant that can be used in, for example, AMR technology, or anyapplication where a barrier to moisture or corrosive liquids is desired.Thus, although the encapsulant is generally described in the context ofutility meter pits, its use is not to be construed as limited to suchtechnology.

Selected combinations of aspects of the disclosed technology correspondto a plurality of different embodiments of the presently disclosedsubject matter. It should be noted that each of the exemplaryembodiments presented and discussed herein should not insinuatelimitations of the presently disclosed subject matter. Features or stepsillustrated or described as part of one embodiment may be used incombination with aspects of another embodiment to yield yet furtherembodiments. Additionally, certain features may be interchanged withsimilar devices, compositions, or features not expressly mentioned whichperform the same or similar function.

Reference will now be made in detail to examples demonstrating the useof the wax-based encapsulant of the present disclosure, followed by adescription of the encapsulant, which exhibits improved moisture barrierproperties. The presently disclosed subject matter in certainembodiments thereof corresponds to a wax-based encapsulant that protectsany electrical components used in AMR technology, although theencapsulant may also be used in other applications where electricalcomponents may need to be protected from a harsh environment, such aswhere moisture or corrosive liquids may be present.

Referring now to the drawings, FIG. 1 illustrates a utility meter pit100 that may contain electronic components coated with the encapsulantof the present disclosure. A utility-meter pit assembly 90 allows accessto below-ground meters, such as a water meter 102 as shown, that areused to measure consumption of water, gas, electricity, and the like.The pit 100 is closed with a lid 101 to protect the equipment inside.Components of a utility meter reading system, such as a cable 104, aradio-frequency (RF) transmitter 108, a leak sensor 110, and the likecan be located in the utility-meter pit 100 and associated with, forexample, a water pipe 105. An AMR device 106 may include an encoder andan integral RF antenna (not shown). Alternatively, these components canbe installed in separate housings and joined with a cable or otherconnector. The AMR device 106, leak sensor 110, and other componentscontain electrical circuitry, which can be damaged if contacted bycorrosive liquids or moisture. While at least the AMR device 106 can beattached to the pit lid 101 so that it is positioned relatively far fromthe bottom of the pit 100 to help keep the AMR device 106 away fromwater and other contaminants that are likely to be present deeper in thepit, the AMR device may still be exposed to extremely humid conditionsand/or corrosive liquids. Additionally, other components such as theleak sensor 110 will inevitably be exposed to moisture and possiblycorrosive liquids. Thus, the wax-based encapsulant of the presentdisclosure can be utilized to protect such components from the intrusionof such moisture and/or corrosive liquids.

With reference to present FIG. 2, there is illustrated an exploded viewof an assembly that includes a detailed view of the electricalcomponents that may be coated with the encapsulant material inaccordance with the present description. FIG. 2 depicts a telemetryantenna system 10 with bulkhead 200. A radome 26 is placed in aninverted position into retainer ring 28, and a seal is formed witho-ring 67. While the radome 26 can weatherproof the telemetry antennasystem 10 associated with a utility meter pit and AMR technology to someextent, there is still moisture within the pit, and it is still possiblethat moisture and corrosive liquids can come into contact withcomponents that encompass the telemetry antenna system 10. Thus, theneed for an improved encapsulant is required as described herein. Theradiator sub-assembly 18, telemetry board 19, and battery 23 are housedwithin the telemetry antenna system in between the radome 26 and end cap30 to protect them from moisture, although there is still the potentialfor the seepage of moisture or corrosive liquids into the telemetryantenna system 10. As shown, the telemetry board 18 and battery 23 restin base 24. Screws 92 are secured to annular plate 36 and retaining ring28 to complete assembly of base 24 to radome 26 and retainer ring 28.

In operation, the radiator sub-assembly 18 receives a signal from ahost. This signal is a wake-up call to the telemetry board 19. Thetelemetry board 19 responds by transmitting, by radio frequency, anidentification signal and meter data from an attached meter, such aswater meter 102 shown in FIG. 1. The transmission from telemetry board19, which is powered by battery 23, is radiated out from radiatorsub-assembly 18 for reception by the host.

With reference to FIG. 3, there is illustrated a perspective view of anelectronic sub-assembly 21 that is also shown as a component of FIG. 2.As is represented by present FIG. 3, the sub-assembly may include abattery 23, a telemetry board 19, and an antenna feed connection 15. Theelectronic sub-assembly is by nature placed in a harsh environment whenit is located in a water meter pit such as pit 100 shown in FIG. 1.Hence, a need exists for the wax-based moisture barrier encapsulant ofthe present disclosure that has low diffusion rates and low waterpermeability, which can protect the electronic sub-assembly from damage.

With reference to present FIG. 4, there is illustrated another type ofelectrical component that may be included in AMR technology. An endpointcircuit board 400 generally incorporating the present encapsulantmaterial 420 is shown. Referring to FIG. 4, an endpoint circuit board400 includes a supporting substrate corresponding to a printed circuitboard (PCB) 410 configured to support and interconnect endpointcomponents including circuitry components 412 and 414 and at least aportion of a two-part antenna coupler 416. The endpoint circuit board400 is shown coated in the encapsulant 420 of the present description.

As illustrated in present FIG. 4, the male portion of the two-partantenna coupler 416 has been mounted to PCB 410, an antenna 430 has beenaffixed to the female portion of two-part antenna coupler 416, and boththe male and female portions as well as an end portion of antenna 430have been coated with encapsulant 420 along with the other components412 and 414 that are mounted to PCB 410. Those of ordinary skill in thepresent art will appreciate that exemplary endpoint 400 may beincorporated into a meter module. In certain instances, such metermodules may be installed in a pit and may be located as deep as 3 to 4feet below local surface level. As many pits for water meters fill withwater, there is thus a need for an improved encapsulant to protect suchcomponents as endpoint 400 from moisture and corrosion.

With reference to present FIG. 5, the improved moisture barrierproperties of the encapsulant of the present disclosure are shown ascompared to a control epoxy-based encapsulant. In addition to improvedmoisture barrier properties, the encapsulant of the present disclosureexhibits low conductivity to avoid shorting out any electricalcomponents that it coats. For example, the dielectric constant, k, ofthe encapsulant can range from about 1.0 to about 10.0, such as fromabout 2.0 to about 8.0, such as from about 4.0 to 6.0 when determined at10 kHz. The low dielectric constant of the encapsulant means that theencapsulant can have a low permittivity, or a low ability to polarizeand hold charge. For this reason, materials such as the describedencapsulant with low dielectric constants can be good insulators forisolating signal-carrying conductors from each other. Thus, theencapsulant can be used in very dense multi-layered integrated circuitsor other electrical devices, wherein coupling between very close metallines need to be suppressed to prevent degradation in deviceperformance. Moreover, the encapsulant does not detrimentally attenuateradio frequency signals used in AMR technology which is due, at least inpart, to the dielectric constant that the encapsulant exhibits.

The encapsulant, which has a melting temperature ranging from about 70°C. to about 80° C., can withstand temperatures of up to about 70° C.without flowing or melting, yet has a low enough viscosity, such as lessthan about 500 centipoise, at a temperature ranging from about 80° C. toabout 95° C. that it can be melted and thereafter dispensed and coatedonto any batteries or other components without causing heat damage tosuch components or shrinkage of the encapsulant. When dispensed at atemperature of from about 80° C. to about 95° C., the encapsulant has aviscosity ranging from about 250 centipoise to about 450 centipoise,such as from about 350 centipoise to about 400 centipoise.

The encapsulant can attach to all relevant surfaces to provide barrierproperties to water vapor and liquid water. As will be discussed, thedata demonstrates the encapsulant of the present disclosure has theability to keep moisture and corrosive liquids out of the electricalcomponents that it surrounds to an extent that is improved from existingtechnology. An exemplary embodiment of an encapsulant material ishereinafter described. The encapsulant material includes a wax and alsocontains other components to take shrinkage and temperature excursionsinto account. For example, in addition to a wax, the encapsulant caninclude a tackifier, a polymer, and a plasticizer. In other embodiments,the encapsulant can further include a thixotropic agent and anantioxidant. These components can all comprise saturated hydrocarbons.Saturated hydrocarbons (alkanes) are the simplest of the hydrocarbonspecies and are composed entirely of single bonds and are saturated withhydrogen. The general formula for saturated hydrocarbons isC_(n)H_(2n+2) (assuming non-cyclic structures). Saturated hydrocarbonsare found as either linear or branched species and have chemicalstability and waterproofing capabilities.

The wax that can be used as the base of the encapsulant material can bea microcrystalline wax that has a melting temperature greater than about65° C., which is the upper operating temperature of the disclosedencapsulant material. Microcrystalline wax is a refined mixture ofsolid, saturated aliphatic hydrocarbons and is produced by de-oilingcertain fractions from the petroleum refining process. Onemicrocrystalline wax that can be used is IGI MICROSERE™ 5799A, availablefrom The International Group, Inc. It has a melting point of about 77°C., a hardness of 28 dmm at 25° C., and a viscosity of 16 mm²/s at 100°C. Although the 5799A wax was used in the encapsulant testing discussedbelow, other similar microcrystalline waxes with similar properties canalso be used, as will be known to those of ordinary skill in the art.For example, other microcrystalline waxes include IGI 5760A, IGI 5715A,IGI 5871A, IGI 5897A, and IGI 5999A. Other microcrystalline waxes withmelting temperatures above the encapsulant operating temperature ofabout 65° C. are available from Clarus Specialty Products of Rock Hill,S.C.

Microcrystalline waxes differ from refined paraffin waxes in that themolecular structure is more branched and the hydrocarbon chains arelonger (higher molecular weight). As a result, the crystal structure ofmicrocrystalline wax is much finer than paraffin wax, and this directlyimpacts many of the physical properties. High melting point paraffinwaxes can also be used, although increased shrinkage of the encapsulantmaterial can result at higher concentrations.

Microcrystalline waxes are tougher, more flexible and generally higherin melting point than paraffin wax. The fine crystal structure alsoenables microcrystalline wax to bind solvents or oil, thus preventingthe sweating-out of compositions. The wax enhances water resistance andcontributes to the sharp solid to liquid transition of the encapsulant.However, using high concentrations of microcrystalline wax can alsocause shrinkage, so its concentration range was determined by takingthis into account.

Another type of wax that can be used is a Fischer-Tropsch wax.Fischer-Tropsch waxes are synthetic waxes produced by Fischer-Tropschprocess. Fischer-Tropsch is a method for the synthesis of hydrocarbonsand other aliphatic compounds from synthesis gas, a mixture of hydrogenand carbon monoxide in the presence of a catalyst. The hydrogen-carbonmonoxide gas mixture is obtained by coal gasification or natural gasreforming. An example of a Fischer-Trope wax is available from Honeywellunder the name A-C® 1702.

Regardless of the specific type of wax base component used in thedescribed encapsulant material, it can be present in a range of fromabout 40% by weight to about 60% by weight of the total encapsulantcomposition, such as from about 45% by weight to about 55% by weight ofthe total encapsulant composition.

Depending on the desired properties, the wax composition andconcentration can vary. For example, a higher concentration range of waxmay increase the operating temperature of the encapsulant to above atemperature of about 65° C.; however, as the concentration of the waxincreases, the amount of shrinkage of the encapsulant can also increase,which may affect the moisture barrier properties of the encapsulant.

In addition to a wax, the encapsulant material can also include atackifier. Tackifiers are chemical compounds used in formulatingadhesives to increase the “tack” or stickiness of a surface of theadhesive. Thus, tackifiers can be used in the encapsulant material toincrease the ability of the encapsulant material to coat and adhere toany electrical components. One tackifier that can be used is NEVTAC® 80(low molecular weight, hydrocarbon resin) which is available fromNeville Chemical Company. This tackifier is a light-colored, lowmolecular weight hydrocarbon resin. It has a softening point of about80° C. and a number average molecular weight of about 990. The resin iscompatible with a wide range of waxes. It has a low molecular weight,gives high tack and low solution viscosities, as well as low moltenviscosities when used in hot-melt adhesives.

Although the NEVTAC® 80 tackifier was used in testing, other similarhydrocarbon resin tackifiers can be used, as will be known to those ofordinary skill in the art. For example, other tackifiers that can beused include STAYBELITE™ Ester 5-C Resin (a glycerol ester ofpartially-hydrogenated rosin), FORAL™ AX-E Fully Hydrogenated Resin (athermoplastic, acidic resin produced by hydrogenating rosin to anexceptionally high degree), FORALYN™ E Partially Hydrogenated Resin(another thermoplastic, acidic resin made by partially hydrogenatingrosin), or FORAL™ 85-E Ester of Hydrogenated Rosin (thermoplastic esterresin derived from glycerol and a highly stabilized rosin), allavailable from Eastman Chemical Company, or QUINTONE™ N180 (an aliphatichydrocarbon resin, C5/C9 type), available from Zeon Chemicals. Theaforementioned tackifiers are either aliphatic (C5) or aromatic (C9)tackifiers. If aromatic tackifiers are used, they can be hydrogenated,which can reduce the moisture vapor transmission rate of the encapsulantmaterial. Using tackifiers with softening points ranging from about 90°C. to about 105° C. can also reduce the moisture vapor transmission rateof the encapsulant material, although this may require higher mixing anddispensing temperatures.

Regardless of the specific type of tackifier used in the describedencapsulant material, it can be present in a range of from about 20% byweight to 40% by weight of the total encapsulant composition, such asfrom about 25% by weight to about 35% by weight of the total encapsulantcomposition and has a softening point of around 80° C. The concentrationrange chosen ensures that the encapsulant does not demonstratebrittleness at lower temperatures.

Additionally, the encapsulant can contain a polymer such as apolyolefin, an ethylene-propylene copolymer, or an isobutylene. Apolyolefin is a polymer produced from a simple olefin (also called analkene with the general formula C_(n)H_(2n)) as a monomer. Beingsaturated hydrocarbons, in general, polyolefins are chemically inert,electrically non-polar, and highly insulating. An equivalent term for apolyolefin is a polyalkene. Polyolefins can be thermoplastic such aspolyalphaolefin, polyethylene (PE), polypropylene (PP),polymethylpentene (PMP), and polybutene-1 (PB-1). Elastomericpolyolefins include polyisobutylene (FIB), ethylene propylene rubber(EPR), and ethylene propylene diene monomer (M-class) rubber (EPDMrubber).

One polyolefin that can be used is VESTOPLAST® 704, which is anamorphous poly-alpha-olefin available from Evonik Degussa GmbH. Thispolyolefin is thermoplastic and is an amorphous polyalphaolefin. It hasa softening point of about 105° C., a melt viscosity of about 3000 mPa sto about 4000 mPa s at 190° C., and can be used to add toughness to theencapsulant. Amorphous polyalphaolefins (APAOs) are polymers ofα-olefins (for example co- and ter-polymers of ethene, propene and1-butene). They can be used for a variety of applications in theadhesives and sealants industry and are especially useful for theproduction of hotmelt adhesives. Although the VESTOPLAST® 704 was usedin testing, other similar polyalphaolefins can be used, as will be knownto those of ordinary skill in the art. Regardless of the specific typeof polyolefin used in the described encapsulant material, it can bepresent in a range of from about 2.5% by weight to about 20% by weightof the total encapsulant composition, such as from about 5% by weight toabout 15% by weight of the total encapsulant composition. Theconcentration range chosen ensures that the encapsulant does notdemonstrate brittleness at low temperatures. Other polymers that can beused include other amorphous poly-alpha-olefins, such as VESTOPLAST® 703and VESTOPLAST® EP NC 702, also available from Evonik Degussa GmbH.Another polyolefin is AFFINITY® GA 1900, which is a low viscositypolyolefin available from Dow Chemical Company.

The polymer can also be an ethylene-propylene copolymer that can furtherbe combined with silica, such as TRILENE FREEFLOW® CP80 available fromLion Copolymer, LLC. The CP80 is a free-flowing ethylene-propylenepolymer made by combining the liquid polymer with silica. The blend canbe 68% ethylene-propylene copolymer and 32% silica.

The polymer can also be a polyisobutylene such as a polymer from theOPPANOL™ B series from BASF.

The encapsulant can also contain a plasticizer to soften the materialand increase tackiness to all surfaces. One plasticizer that can be usedto soften the encapsulant resin is polyisobutylene, which is anelastomeric polyolefin as discussed above. Polyisobutylene, also knownas “PIB” or polyisobutene, (C₄H₈)_(n), is the homopolymer ofisobutylene, or 2-methyl-1-propene, on which butyl rubber is based.Structurally, polyisobutylene resembles polypropylene, having two methylgroups substituted on every other carbon atom. Polyisobutylene is acolorless to light yellow viscoelastic material. It is generallyodorless and tasteless, though it may exhibit a slight characteristicodor. It has excellent impermeability, and the long polyisobutylenesegments of its polymer chains give it good flex properties.

Polyisobutylene is available from Texas Petrochemical Company as TPC1105. Although TPC 1105 was used in testing, other polyisobutylenes canbe used, as will be known to those of ordinary skill in the art, such aspolyisobutylenes having a molecular weight of from about 500 to about2500 grams/mole. Another example of a polyisobutylene that can be usedas a plasticizer is INDOPOL™ H35, available from INEOS Oligomers.Regardless of the specific type of plasticizer used in the encapsulant,it can be present in a range of from about 5% by weight to about 25% byweight of the total encapsulant composition, such as from about 8% byweight to about 12% by weight of the total encapsulant composition.

Another component of the encapsulant may be a thixotropic agent. Athixotropic agent can be added to reduce the likelihood that theencapsulant will flow at higher operating temperatures. One thixotropicagent that can be used in the encapsulant of the present disclosure isSIPERNAT® D13, which is available from Evonik Degussa GmbH. SIPERNAT®D13 is a fine particle hydrophobic precipitated silica. Hydrophobicsilica is a silica that has hydrophobic groups chemically bonded to thesurface. Hydrophobic silica can be made both from fumed and precipitatedsilica. The hydrophobic groups are normally alkyl orpolydimethylsiloxane chains.

Although SIPERNAT® D13 was used as the thixotropic agent during testingof the encapsulant, other agents can be used, as will be known to thoseof ordinary skill in the art, such as other hydrophobic (fumed orprecipitated) silicas or silica powders, which enable the agents todissolve in the molten wax resin. Other examples of silica powders thatcan be used include SIPERNAT® D10, SIPERNAT® D11, SIPERNAT® D13, andSIPERNAT® D17, all available from Evonik Degussa GmbH. Anotherthixotropic agent that can be used is CAB-O-SILO TS-720 Fumed Silica,available from Cabot Corporation. In any event, a thixotropic agent witha low surface area can be used since it can be added in higherconcentrations without significantly raising the melt viscosity of thefinal resin, which could result in higher temperatures that can bedamaging to any encapsulated electrical components.

Regardless of the type of thixotropic agent used in the encapsulant, itcan be present in a range of from about 0.25% by weight to about 1.50%by weight of the total encapsulant composition, such as from about 0.50%by weight to about 1.00% by weight of the total encapsulant composition.The concentration by weight should be less than 1.50% of the totalencapsulant composition in order to maintain a low enough melt viscosityat dispensing temperatures ranging from about 80° C. to about 90° C.

One more component of the encapsulant may be an antioxidant used toprevent oxidation of the resin. Antioxidants are widely used to preventthe oxidative degradation of polymers such as rubbers, plastics andadhesives that causes a loss of strength and flexibility in thesematerials. Polymers containing double bonds in their main chain can beespecially susceptible to oxidation. One antioxidant that can be used inthe encapsulant of the present disclosure is NA-Lube AO 220 (BHT),available from King Industries. This phenolic antioxidant has thechemical composition 2,6 di-tert-butyl-p-cresol and is a 100% activephenolic antioxidant. It is a general purpose antioxidant with a lowmelting point of about 69° C. that liquefies with minimal heat.

Although NA-Lube AO 220 (BHT) was used as the antioxidant during testingof the encapsulant composition, other phenolic antioxidants, aromaticamines, or gallic acid esters can be used, as will be known to those ofordinary skill in the art. Regardless of the type of antioxidant used inthe encapsulant, it can be present in a range of about 0.01% to 0.20% byweight.

Generally, the encapsulant material is made by mixing the componentsabove via impeller mixing at a temperature ranging from about 90° C. toabout 120° C. The higher temperatures can facilitate and accelerate thedispersion of the polymer. After the encapsulant is mixed, it can bedispensed around any desired electrical components at a temperatureranging from about 80° C. to about 95° C. or lower. Any electricalcomponents can also be preheated to a temperature ranging from about 80°C. to about 95° C., which can prevent shrinkage or pulling away of theencapsulant from the electrical components after cooling due totemperature mismatch. After the encapsulant has been dispensed around anelectronic component to form a coating, the coated electronic component,which is now encapsulated, can be allowed to harden and cool before use.

An example encapsulant formed from the components described above hasbeen tested alongside an epoxy-based control to determine moisturebarrier properties as compared to the control. Table 1 summarizes thecomponents of the encapsulant used in testing:

TABLE 1 Tested Encapsulant Components Role in Weight ComponentName/Supplier Formulation % Microcrystalline IGI-5799 MICROSERE ™, Basematerial 49.90 Wax The International Group, Inc. Tackifier NEVTAC ® 80,Neville Improves adhesion 29.25 Chemical Company Polymer VESTOPLAST ®704, Adds toughness 10.00 Evonik Degussa GmbH Plasticizer TPC 1105,Texas Softens resin 10.00 Petrochemical Company Thixotropic SIPERNAT ®D13, Arrests flow at  0.75 Agent Evonik Degussa GmbH higher temperaturesAntioxidant NA-Lube AO 220 (BHT), Prevents oxidation  0.10 KingIndustries

In the test, the epoxy-based control was coated with the encapsulant asdescribed in Table 1 to form the test sample, which was compared to theepoxy-based control with no coating. The percent weight gain, which canbe attributed to the diffusion of moisture through the encapsulant ofthe present disclosure and the control, was measured over a length oftime at varying temperatures and relative humidities. The results of thetesting are shown in FIG. 5. As evidenced by FIG. 5, the test samplescoated with the encapsulant of the present disclosure exhibitedsignificantly lower percent weight gain than the controls, signalingtheir improved moisture barrier properties, which can be associated witha lower permeability and a lower moisture vapor transmission rate.Generally, the percent weight gain due to moisture of the encapsulantmaterial ranges from about 0.001% by weight to about 1.5% by weight. Thepercent weight gain at 200 days at 35° C. and 95% relative humidity canrange from about 0.001% by weight to about 0.75% by weight. The percentweight gain at 200 days at 70° C. and 85% relative humidity can rangefrom about 0.05% by weight to about 1.5% by weight. Meanwhile, thepercent weight gain at 200 days at under cyclic testing ranging from−40° C. to 70° C. and relative humidities ranging from 0% to 85% canrange from about 0.001% by weight to about 0.75% by weight.

More specifically, the encapsulant of the present disclosure and theepoxy control were tested for their moisture barrier properties underthree testing conditions. Under testing condition 1, the materials weremonitored over a period of about 200 days at 35° C. and 95% relativehumidity. By 400 days, the epoxy control, shown as label 3 on FIG. 5,exhibited a percent weight gain of about 20%. Meanwhile, the two samplescoated with the encapsulant as described in Table 1 and shown as labels1 and 2 on FIG. 5, exhibited a percent weight gain on average of lessthan about 0.15%. This demonstrates that the encapsulant of the presentdisclosure can provide for improved moisture barrier properties overcurrent potting materials, such as a reduced moisture vapor transmissionrate over current potting materials, such as the epoxy control, as shownby the small % weight gain due to moisture of the described encapsulantmaterial.

Next, under testing condition 2, the materials were monitored over aperiod of about 200 days at 70° C. and 85% relative humidity. By 200days, the epoxy control, shown as label 6 on FIG. 5, exhibited a percentweight gain of about 15%. On the other hand, the two samples coated withthe encapsulant of the present disclosure as described in Table 1, shownas labels 4 and 5 on FIG. 5, exhibited a percent weight gain on averageof less than about 0.5%. Again, this demonstrates that the encapsulantof the present disclosure can provide for improved moisture barrierproperties, such as a reduced water vapor transmission rate over currentpotting materials, such as the epoxy control, as shown by the small %weight gain due to moisture of the described encapsulant material.

Under testing condition 3, the encapsulant of the present disclosure andthe control were monitored over a period of about 200 days under 12-hourcyclic testing where the samples were held at 25° C. and 35% relativehumidity for 2.5 hours. After this time, the conditions were ramped upto 70° C. and 85% relative humidity over a period of 0.5 hours, afterwhich time the samples were held at 70° C. and 85% humidity for 2.5hours. Next, the samples were subjected to a decrease to 25° C. and 35%relative humidity over a period of 0.5 hours, after which time thesamples were held at 25° C. and 35% relative humidity for 2.5 hours.Next, the samples were subjected to a decrease to −40° C. and 0%relative humidity over a period of 0.5 hours, after which time thesamples were held at −40° C. and 0% relative humidity for 2.5 hours.Finally, the samples were returned to the starting conditions of 25° C.and 35% relative humidity over a period of 0.5 hours. This cycle wasrepeated over the course of about 200 days, as shown in FIG. 5. By 200days, the epoxy control, shown as label 9 on FIG. 5, exhibited a percentweight gain of about 2.3%. In contrast, the samples coated with theencapsulant of the present disclosure, shown as labels 7 and 8 on FIG.5, exhibited a percent weight gain on average of about 0.18%. Thus,under constant humidity and temperature, as well as under cyclichumidity and temperature, the test samples coated with the encapsulantof the present disclosure exhibited almost no percent weight gain,indicating a lower water vapor transmission rate than the control andalmost 100% waterproof characteristics. Table 2 summarizes the datadiscussed above:

TABLE 2 Percent Weight Gain of Tested Encapsulant and Control, 200 DaysLabel Number Sample Test Conditions % Weight Gain 1 Encapsulant 35° C.,95% Humidity 0.15 2 Encapsulant 35° C., 95% Humidity 0.15 3 Control 35°C., 95% Humidity 20 4 Encapsulant 70° C., 85% Humidity 0.5 5 Encapsulant70° C., 85% Humidity 0.5 6 Control 70° C., 85% Humidity 15 7 EncapsulantCyclic 0.18 8 Encapsulant Cyclic 0.18 9 Control Cyclic 2.3

While the presently disclosed subject matter has been described indetail with respect to specific embodiments thereof, it will beappreciated that those skilled in the art, upon attaining anunderstanding of the foregoing may readily produce alterations to,variations of, and equivalents to such embodiments. Accordingly, thescope of the present disclosure is by way of example rather than by wayof limitation, and the subject disclosure does not preclude inclusion ofsuch modifications, variations and/or additions to the presentlydisclosed subject matter and appended claims as would be readilyapparent to one of ordinary skill in the art.

1-20. (canceled)
 21. An encapsulant for use with electronic componentsused in automatic meter reading technology operating at temperatures ofless than about 65° C., comprising: a wax, wherein the wax is present inan amount ranging from about 40% by weight to about 60% by weight of theencapsulant; a tackifier; a polymer; a plasticizer; and an antioxidant;wherein the encapsulant has a melting temperature ranging from about 70°C. to about 80° C., wherein the encapsulant exhibits a percent weightgain of from about 0.001% by weight to about 1.5% by weight over aperiod of about 200 days, wherein the temperature ranges from about −40°C. to about 70° C., and wherein the relative humidity ranges from about0% to about 85%.
 22. (canceled)
 23. An encapsulant as in claim 21,wherein the wax comprises a microcrystalline wax, a paraffin wax, or aFischer-Tropsch wax.
 24. An encapsulant as in claim 21, wherein thetackifier is present in an amount ranging from about 20% by weight toabout 40% by weight of the encapsulant.
 25. An encapsulant as in claim21, wherein the tackifier comprises a hydrocarbon resin; a glycerolester of partially hydrogenated rosin; a thermoplastic, acidic resin; ora thermoplastic ester resin.
 26. An encapsulant as in claim 21, whereinthe polymer is present in an amount ranging from about 2.5% by weight toabout 20% by weight of the encapsulant.
 27. An encapsulant as in claim21, wherein the polymer comprises a polyolefin, an ethylene-propylenecopolymer, or an isobutylene.
 28. An encapsulant as in claim 21, whereinthe plasticizer is present in an amount ranging from about 5% by weightto about 25% by weight of the encapsulant.
 29. An encapsulant as inclaim 21, wherein the plasticizer comprises a polyisobutylene having amolecular weight ranging from about 500 g/mole to about 2500 g/mole. 30.An encapsulant as in claim 21, wherein the antioxidant is present in anamount ranging from about 0.01% by weight to about 0.20% by weight ofthe encapsulant.
 31. An encapsulant as in claim 21, wherein theantioxidant comprises a phenolic antioxidant.
 32. (canceled)
 33. Anencapsulant as in claim 21, wherein the encapsulant has a dispensingtemperature ranging from about 80° C. to about 95° C.
 34. An encapsulantas in claim 21, wherein the encapsulant has a viscosity ranging fromabout 250 centipoise to about 450 centipoise when dispensed.
 35. Anencapsulant as in claim 21, wherein the encapsulant has a dielectricconstant ranging from about 2.0 to about 8.0.
 36. An encapsulant as inclaim 21, wherein the encapsulant further comprises a thixotropic agent.37. An encapsulant as in claim 36, wherein the thixotropic agent ispresent in an amount ranging from about 0.25% by weight to about 1.5% byweight.
 38. An encapsulant as in claim 36, wherein the thixotropic agentcomprises a hydrophobic silica.